import { normalizeSessions, readError } from './utils'
import type { QueryClient } from '@tanstack/react-query'
import type {
  GatewayMessage,
  HistoryResponse,
  SessionListResponse,
  SessionMeta,
} from './types'

type GatewayStatusResponse = {
  ok: boolean
  error?: string
  status?: number
}

function normalizeId(value: unknown): string {
  if (typeof value !== 'string') return ''
  const trimmed = value.trim()
  return trimmed.length > 0 ? trimmed : ''
}

function getMessageClientId(message: GatewayMessage): string {
  const raw = message as Record<string, unknown>
  const candidates = [raw.clientId, raw.client_id]
  for (const candidate of candidates) {
    const normalized = normalizeId(candidate)
    if (normalized) return normalized
  }
  return ''
}

function getMessageOptimisticId(message: GatewayMessage): string {
  return normalizeId(message.__optimisticId)
}

function isMatchingClientMessage(
  message: GatewayMessage,
  clientId: string,
  optimisticId: string,
): boolean {
  const messageClientId = getMessageClientId(message)
  if (messageClientId === clientId) return true

  const messageOptimisticId = getMessageOptimisticId(message)
  if (!messageOptimisticId) return false
  if (messageOptimisticId === clientId) return true
  if (messageOptimisticId === optimisticId) return true
  return false
}

export const chatQueryKeys = {
  sessions: ['chat', 'sessions'] as const,
  history: function history(friendlyId: string, sessionKey: string) {
    return ['chat', 'history', friendlyId, sessionKey] as const
  },
} as const

export async function fetchSessions(): Promise<Array<SessionMeta>> {
  const res = await fetch('/api/sessions')
  if (!res.ok) throw new Error(await readError(res))
  const data = (await res.json()) as SessionListResponse
  return normalizeSessions(data.sessions)
}

export async function fetchHistory(payload: {
  sessionKey: string
  friendlyId: string
}): Promise<HistoryResponse> {
  const query = new URLSearchParams({ limit: '1000' })
  if (payload.sessionKey) query.set('sessionKey', payload.sessionKey)
  if (payload.friendlyId) query.set('friendlyId', payload.friendlyId)
  const res = await fetch(`/api/history?${query.toString()}`)
  if (!res.ok) throw new Error(await readError(res))
  return (await res.json()) as HistoryResponse
}

export async function fetchGatewayStatus(): Promise<GatewayStatusResponse> {
  const controller = new AbortController()
  const timeout = window.setTimeout(() => controller.abort(), 5000)

  try {
    const res = await fetch('/api/ping', { signal: controller.signal })
    if (!res.ok) {
      const error = new Error(await readError(res)) as Error & {
        status?: number
      }
      error.status = res.status
      throw error
    }
    const payload = (await res.json()) as GatewayStatusResponse
    return {
      ...payload,
      status: res.status,
    }
  } catch (err) {
    if (err instanceof DOMException && err.name === 'AbortError') {
      throw new Error('Gateway check timed out')
    }
    throw err
  } finally {
    window.clearTimeout(timeout)
  }
}

export function updateHistoryMessages(
  queryClient: QueryClient,
  friendlyId: string,
  sessionKey: string,
  updater: (messages: Array<GatewayMessage>) => Array<GatewayMessage>,
) {
  const queryKey = chatQueryKeys.history(friendlyId, sessionKey)
  queryClient.setQueryData(queryKey, function update(data: unknown) {
    const current = data as HistoryResponse | undefined
    const messages = Array.isArray(current?.messages) ? current.messages : []
    const nextMessages = updater(messages)
    return {
      sessionKey: current?.sessionKey ?? sessionKey,
      sessionId: current?.sessionId,
      messages: nextMessages,
    }
  })
}

/**
 * Extract normalized plain text content from a GatewayMessage for dedup
 * comparison. Handles both content-array and legacy text/message fields.
 */
function normalizeMessageText(message: GatewayMessage): string {
  const raw = message as Record<string, unknown>

  // Prefer structured content array (canonical format)
  if (Array.isArray(message.content)) {
    const text = message.content
      .map((part) => {
        if (part.type === 'text') return String(part.text ?? '')
        return ''
      })
      .join('')
      .trim()
    if (text.length > 0) return text
  }

  // Fall back to legacy top-level text/message fields (some gateway / channel
  // adapters use these instead of the content-array format)
  for (const key of ['text', 'message', 'body']) {
    const val = raw[key]
    if (typeof val === 'string' && val.trim().length > 0) return val.trim()
  }

  return ''
}

/**
 * Build an attachment identity signature for image-only dedup.
 * Uses name + size because those survive the round-trip through the gateway;
 * the base64 content is stripped before storage/history.
 */
function normalizeAttachmentSignature(message: GatewayMessage): string {
  const raw = message as Record<string, unknown>
  const attachments = Array.isArray(raw.attachments)
    ? (raw.attachments as Array<Record<string, unknown>>)
    : []
  if (attachments.length === 0) return ''
  return attachments
    .map((a) => `${String(a.name ?? '')}:${String(a.size ?? '')}`)
    .sort()
    .join('|')
}

function replaceMatchingOptimisticUserMessage(
  messages: Array<GatewayMessage>,
  incomingMessage: GatewayMessage,
): Array<GatewayMessage> | null {
  if (incomingMessage.role !== 'user') return null

  const incomingClientId = getMessageClientId(incomingMessage)
  const incomingOptimisticId = getMessageOptimisticId(incomingMessage)
  const incomingText = normalizeMessageText(incomingMessage)
  const incomingAttachSig = normalizeAttachmentSignature(incomingMessage)
  const nowMs = Date.now()
  const TEN_SECONDS = 10_000

  const matchIndex = messages.findIndex((message) => {
    if (message.role !== 'user') return false

    const raw = message as Record<string, unknown>
    const isOptimistic =
      typeof raw.__optimisticId === 'string' && raw.__optimisticId.length > 0
    if (!isOptimistic) return false

    if (
      incomingClientId &&
      isMatchingClientMessage(
        message,
        incomingClientId,
        incomingOptimisticId || `opt-${incomingClientId}`,
      )
    ) {
      return true
    }

    if (!incomingText && !incomingAttachSig) return false

    const textMatch =
      incomingText.length > 0 && normalizeMessageText(message) === incomingText
    const attachMatch =
      incomingAttachSig.length > 0 &&
      normalizeAttachmentSignature(message) === incomingAttachSig
    const isContentMatch =
      (incomingText.length > 0 && textMatch) ||
      (incomingText.length === 0 && incomingAttachSig.length > 0 && attachMatch)

    if (!isContentMatch) return false

    const timestamp =
      typeof raw.timestamp === 'number' && Number.isFinite(raw.timestamp)
        ? raw.timestamp
        : null
    if (timestamp !== null) {
      return nowMs - timestamp < TEN_SECONDS
    }

    const idx = messages.indexOf(message)
    return idx >= messages.length - 5
  })

  if (matchIndex === -1) return null

  const existing = messages[matchIndex]
  const replacement: GatewayMessage = {
    ...existing,
    ...incomingMessage,
    clientId: incomingClientId || getMessageClientId(existing) || undefined,
    client_id: incomingClientId || getMessageClientId(existing) || undefined,
    __optimisticId: undefined,
    status: undefined,
  }

  const next = [...messages]
  next[matchIndex] = replacement
  return next
}

export function appendHistoryMessage(
  queryClient: QueryClient,
  friendlyId: string,
  sessionKey: string,
  message: GatewayMessage,
) {
  updateHistoryMessages(
    queryClient,
    friendlyId,
    sessionKey,
    function append(messages) {
      const replacedOptimistic = replaceMatchingOptimisticUserMessage(
        messages,
        message,
      )
      if (replacedOptimistic) return replacedOptimistic

      // Dedup: if a message with the same clientId (or optimistic id) already
      // exists, skip appending — prevents double-display when an optimistic
      // message is added on send and then echoed back via SSE onUserMessage.
      const incomingClientId = getMessageClientId(message)
      const incomingOptimisticId = getMessageOptimisticId(message)
      if (incomingClientId || incomingOptimisticId) {
        const optimisticKey = incomingClientId ? `opt-${incomingClientId}` : ''
        const alreadyExists = messages.some((m) =>
          isMatchingClientMessage(
            m,
            incomingClientId || incomingOptimisticId,
            optimisticKey || incomingOptimisticId,
          ),
        )
        if (alreadyExists) return messages
      }

      // Fallback dedup for SSE-echoed user messages that arrive WITHOUT a
      // clientId (gateway did not echo it back). Check if an existing optimistic
      // user message with the same text content (or attachment signature for
      // image-only sends) was added in the last 10 seconds. This prevents
      // duplicates without dropping legitimately repeated messages sent at
      // longer intervals.
      if (message.role === 'user' && !incomingClientId && !incomingOptimisticId) {
        const incomingText = normalizeMessageText(message)
        const incomingAttachSig = normalizeAttachmentSignature(message)
        // Only apply dedup if there is SOME identity to match against
        if (incomingText.length > 0 || incomingAttachSig.length > 0) {
          const nowMs = Date.now()
          const TEN_SECONDS = 10_000
          const isDuplicate = messages.some((m) => {
            if (m.role !== 'user') return false

            // Determine if this candidate is a content match:
            // • Text messages: compare normalised text
            // • Image-only messages: compare attachment signatures
            // • Mixed (text + image): text takes priority; attachment sig is a
            //   secondary signal used only when text also matches
            const textMatch =
              incomingText.length > 0 && normalizeMessageText(m) === incomingText
            const attachMatch =
              incomingAttachSig.length > 0 &&
              normalizeAttachmentSignature(m) === incomingAttachSig

            const isContentMatch =
              (incomingText.length > 0 && textMatch) ||
              (incomingText.length === 0 && incomingAttachSig.length > 0 && attachMatch)

            if (!isContentMatch) return false

            // If we have timestamps, check recency; otherwise check the last
            // few recent messages (optimistic messages are at the tail).
            const msgTimestamp =
              typeof m.timestamp === 'number' ? m.timestamp : null
            if (msgTimestamp !== null) {
              return nowMs - msgTimestamp < TEN_SECONDS
            }
            // No timestamps — check if this is one of the last 5 messages
            // (optimistic messages are always appended at the end)
            const idx = messages.indexOf(m)
            return idx >= messages.length - 5
          })
          if (isDuplicate) return messages
        }
      }

      // Insert in timestamp order so that late-arriving SSE echoes (e.g. a
      // user message whose echo arrives after the assistant reply is already
      // displayed) appear in the correct chronological position rather than
      // being appended to the bottom of the list.
      const incomingTs =
        typeof (message as Record<string, unknown>).timestamp === 'number'
          ? (message as Record<string, unknown>).timestamp as number
          : null

      if (incomingTs !== null) {
        // Find the first existing message whose timestamp is strictly greater
        // than the incoming message — insert before it.
        const insertIdx = messages.findIndex((m) => {
          const ts = typeof (m as Record<string, unknown>).timestamp === 'number'
            ? (m as Record<string, unknown>).timestamp as number
            : null
          return ts !== null && ts > incomingTs
        })
        if (insertIdx >= 0) {
          const next = [...messages]
          next.splice(insertIdx, 0, message)
          return next
        }
      }

      return [...messages, message]
    },
  )
}

export function updateHistoryMessageByClientId(
  queryClient: QueryClient,
  friendlyId: string,
  sessionKey: string,
  clientId: string,
  updater: (message: GatewayMessage) => GatewayMessage,
) {
  const normalizedClientId = normalizeId(clientId)
  if (!normalizedClientId) return
  const optimisticId = `opt-${normalizedClientId}`
  updateHistoryMessages(
    queryClient,
    friendlyId,
    sessionKey,
    function update(messages) {
      return messages.map((message) => {
        if (
          isMatchingClientMessage(message, normalizedClientId, optimisticId)
        ) {
          return updater(message)
        }
        return message
      })
    },
  )
}

export function updateHistoryMessageByClientIdEverywhere(
  queryClient: QueryClient,
  clientId: string,
  updater: (message: GatewayMessage) => GatewayMessage,
) {
  const normalizedClientId = normalizeId(clientId)
  if (!normalizedClientId) return
  const optimisticId = `opt-${normalizedClientId}`
  const historyQueries = queryClient.getQueriesData<HistoryResponse>({
    queryKey: ['chat', 'history'],
  })

  for (const [queryKey, data] of historyQueries) {
    const current = data as HistoryResponse | undefined
    const messages = Array.isArray(current?.messages) ? current.messages : []
    let changed = false
    const nextMessages = messages.map((message) => {
      if (!isMatchingClientMessage(message, normalizedClientId, optimisticId)) {
        return message
      }
      changed = true
      return updater(message)
    })
    if (!changed) continue
    queryClient.setQueryData(queryKey, {
      sessionKey: current?.sessionKey ?? '',
      sessionId: current?.sessionId,
      messages: nextMessages,
    })
  }
}

export function removeHistoryMessageByClientId(
  queryClient: QueryClient,
  friendlyId: string,
  sessionKey: string,
  clientId: string,
  optimisticId?: string,
) {
  const normalizedClientId = normalizeId(clientId)
  if (!normalizedClientId) return
  const resolvedOptimisticId =
    normalizeId(optimisticId) || `opt-${normalizedClientId}`

  updateHistoryMessages(
    queryClient,
    friendlyId,
    sessionKey,
    function remove(messages) {
      return messages.filter((message) => {
        return !isMatchingClientMessage(
          message,
          normalizedClientId,
          resolvedOptimisticId,
        )
      })
    },
  )
}

export function clearHistoryMessages(
  queryClient: QueryClient,
  friendlyId: string,
  sessionKey: string,
) {
  const queryKey = chatQueryKeys.history(friendlyId, sessionKey)
  queryClient.setQueryData(queryKey, {
    sessionKey,
    messages: [],
  })
}

export function moveHistoryMessages(
  queryClient: QueryClient,
  fromFriendlyId: string,
  fromSessionKey: string,
  toFriendlyId: string,
  toSessionKey: string,
) {
  const fromKey = chatQueryKeys.history(fromFriendlyId, fromSessionKey)
  const toKey = chatQueryKeys.history(toFriendlyId, toSessionKey)
  const fromData = queryClient.getQueryData(fromKey) as
    | Record<string, unknown>
    | undefined
  if (!fromData) return
  const messages = Array.isArray(fromData.messages) ? fromData.messages : []
  queryClient.setQueryData(toKey, {
    sessionKey: toSessionKey,
    sessionId: (fromData as any).sessionId,
    messages,
  })
  queryClient.removeQueries({ queryKey: fromKey, exact: true })
}

export function updateSessionLastMessage(
  queryClient: QueryClient,
  sessionKey: string,
  friendlyId: string,
  message: GatewayMessage,
) {
  queryClient.setQueryData(
    chatQueryKeys.sessions,
    function update(messages: unknown) {
      if (!Array.isArray(messages)) return messages
      return (messages as Array<SessionMeta>).map((session) => {
        if (session.key !== sessionKey && session.friendlyId !== friendlyId) {
          return session
        }
        return {
          ...session,
          lastMessage: message,
        }
      })
    },
  )
}

export function removeSessionFromCache(
  queryClient: QueryClient,
  sessionKey: string,
  friendlyId: string,
) {
  queryClient.setQueryData(
    chatQueryKeys.sessions,
    function update(messages: unknown) {
      if (!Array.isArray(messages)) return messages
      return (messages as Array<SessionMeta>).filter((session) => {
        return session.key !== sessionKey && session.friendlyId !== friendlyId
      })
    },
  )

  queryClient.removeQueries({
    queryKey: ['chat', 'history', friendlyId],
    exact: false,
  })
  if (sessionKey && sessionKey !== friendlyId) {
    queryClient.removeQueries({
      queryKey: ['chat', 'history', sessionKey],
      exact: false,
    })
  }
}
